Construction machinery

ABSTRACT

A construction machine which is less vulnerable to theft compared with conventional machines is provided. The system includes an antenna ( 6 ) for detecting removal of an engine key ( 8 ) after the engine has stopped, an angle detector ( 35 ) for detecting a posture of the upper structure, and an anti-theft unit ( 31 ) for forcing the engine to stop and outputting an alarm signal in cases the upper structure is not in a given posture when parked.

TECHNICAL FIELD

[0001] The present invention relates to a construction machine equippedwith an anti-theft means.

BACKGROUND OF THE INVENTION

[0002] A construction machine, such as a hydraulic excavator, istypically equipped with an engine, which serves as a power source, andan operator's cab, which is provided with operation switches forperforming various works, including starting or stopping the engine.Unlike automobiles, construction machines are normally designed to beoperated with a common engine key so that an operator can operate aplurality of construction machines with a single type of key. This,however, makes construction machines vulnerable to theft or tampering.In order to solve this problem, a construction machine is usuallyequipped with an anti-theft system.

[0003]FIG. 11 shows a block diagram of an example of conventionalanti-theft systems. FIG. 12 is a control block diagram of an anti-theftunit of said anti-theft system. FIG. 13 is a system block diagram of ahydraulic excavator, which is employed herein as an example ofconstruction machines.

[0004] As shown in FIG. 11, a starter switch 10 is provided. The starterswitch 10 serves to start or stop the engine by switching the electricpower, which is supplied from a battery 9 as a result of operation ofthe engine key 8. A main relay 11, which is adapted to be energized bythe starter switch 10, is connected to an engine start-up relay 12 and asolenoid valve relay 13. The main relay 11 is adapted to be turned on oroff by operating the starter switch 10 so as to supply electric power tovarious components of the main body of the construction machine, whichare not shown in the drawings.

[0005] Connected to the solenoid valve relay 13 is a hydraulic lockingswitch 14 to be operated by an operator when the machine is beingdriven. The hydraulic locking switch 14 is for ensuring safety by beingkept in the off position when the machine is not being operated.

[0006] A starter motor 15 for starting up the engine is connected to theengine start-up relay 12. A solenoid-operated directional control valve16 for controlling the direction of pressurized pilot oil is connectedto the solenoid valve relay 13. Numeral 17 denotes a ground wire.

[0007] The anti-theft system mainly comprises an anti-theft unit 1, anantenna 6, and an identification tag 7 (the term ‘identification’ willhereinafter be abbreviated as ‘ID’). The antenna 6 is incorporated inthe starter switch 10. The ID tag 7 is for identifying an individual andattached to an engine key 8.

[0008] The anti-theft unit 1 includes a control unit 2, a power supplyunit 3, and relays 4,5, which are adapted to be controlled by outputfrom the control unit 2.

[0009]FIG. 12 is a control block diagram of the control unit 2. Thecontrol unit 2 is provided with an ID code determining unit 20 and an IDcode storage unit 21 connected to the ID code determining unit 20. TheID code storage unit 21 is for identifying an individual machine.

[0010] By means of radio communication between the antenna 6 and the IDtag 7, the ID code of the ID tag 7 is read into the control unit 2. Thecontrol unit 2 is adapted to receive ACC contact signals from thestarter switch 10; when the ACC contact of the starter switch 10 is on,the ID code determining unit 20 functions to collate the ID code of theID tag 7 with the ID code stored in the ID code storage unit 21, and,according to the result of collation, the relays 4,5 are activated.

[0011] Referring to FIG. 13, pressurized oil fed from a main pump 23,which is adapted to be driven by the engine 22, is controlled anddistributed to hydraulic cylinders 25 by control valves 24. The circuitpressure in a pump discharge circuit is limited by a relief valve 26.

[0012] A pilot pump 27 driven by the engine 22 discharges pressurizedpilot oil, which is fed to the aforementioned solenoid-operateddirectional control valve 16. The solenoid-operated directional controlvalve 16 determines whether the pilot oil should be fed tosolenoid-operated directional control valves 28 a,28 b,28 c ordischarged into a tank. The solenoid-operated directional control valves28 a,28 b,28 c are remote control valves for controlling the controlvalves 24. The pilot pressure is held at a certain constant level by apilot pressure relief valve 29.

[0013] Next, the function of the example of conventional anti-theftsystems described above is explained hereunder.

[0014] Referring to FIG. 11, when the engine key 8, to which an ID tag 7is attached, is inserted into the starter switch 10 and turned from theOFF position to the ACC position, radio communication is activatedbetween the antenna 6 and the ID tag 7 so that the ID code associatedwith the ID tag 7 is read into the anti-theft unit 1.

[0015] The ID code determining unit 20 of the control unit 2 shown inFIG. 12 collates the ID code of the ID tag 7 with the ID code stored inthe ID code storage unit 21. If the two ID codes match, an ON signal isoutput from the ID code determining unit 20 so that the engine start-uprelay 12 and the solenoid valve relay 13 are energized via the relays4,5.

[0016] When the starter switch 10 is turned to the start-up position STin the state described above, an electric current is supplied to thestarter motor 15 via the main relay 11 and the engine start-up relay 12so that the engine 22 starts up.

[0017] Should the operator turn on the hydraulic locking switch 14, thesolenoid-operated directional control valve 16 switches over fromchamber n to chamber a so as to feed the pressurized oil from the pilotpump 27 to the remote control valves 28. By operating the remote controlvalves 28, the directional control valves 24 can be changed over so thatthe pressurized oil from the main pump 23 is fed to the appropriatehydraulic cylinders 25.

[0018] Because of the function described above, an operator can drivethe construction machine by using an engine key 8 to which a registeredID tag 7 is attached.

[0019] Should an attempt be made to start the engine with an engine key8 having an unregistered ID tag 7 or having no ID tag 7 at all, neitherthe engine start-up relay 12 nor the solenoid valve relay 13 will beenergized, because the ID codes do not match. As a result, it becomesimpossible to start the engine or operate the construction machine.

[0020] When the anti-theft unit 1 of a conventional anti-theft system isinstalled at a place that allows easy installation, it is easy todisable the anti-theft unit 1 by removing the unit or cutting a cable.

[0021] Another problem of the conventional system described above liesin that the system permits start-up of the engine by merely checking IDcodes; it is vulnerable to theft, because the engine 22 can be startedby connecting the plus line of the battery 9 directly to the startermotor 15.

[0022] In order to solve the above problems, an object of the inventionis to provide a construction machine which is less vulnerable to theftcompared with conventional construction machines.

DISCLOSURE OF THE INVENTION

[0023] A construction machine according to the present inventionincludes a machine body, an engine which serves as a power source forthe machine body, a key-removal detecting means for detecting removal ofthe engine key after the engine is stopped, a posture detecting meansfor detecting a posture of the machine body, and an anti-theft meansadapted to output an alarm signal in cases where the machine body fromwhich the engine key has been removed is not in a given, proper parkingposture. In the event the machine body is put into motion byunauthorized start-up of the engine without using the engine key, such asituation is detected by the key-removal detecting means and the posturedetecting means, and an alarm signal is output by the anti-theft means.Therefore, compared with conventional art, the invention is capable ofreducing the possibility of theft of the construction machine.

[0024] A construction machine according to another feature of thepresent invention includes an undercarriage, an upper structurerotatably mounted on the undercarriage, an engine which serves as apower source for the undercarriage and the upper structure, akey-removal detecting means for detecting removal of the engine keyafter the engine is stopped, a posture detecting means for detecting arotated posture of the upper structure, and an anti-theft means adaptedto output an alarm signal when the upper structure from which the enginekey has been removed is not in a given, proper parking posture. In theevent the upper structure is put into motion by unauthorized start-up ofthe engine without using the engine key, such a situation is detected bythe key-removal detecting means and the posture detecting means, and analarm signal is output by the anti-theft means. Therefore, compared withconventional art, the invention is capable of reducing the possibilityof theft of the construction machine.

[0025] The anti-theft means of a construction machine according to yetanother feature of the present invention is designed to prevent theengine from starting up and output an alarm signal when any engine keyother than an engine key that permits identification of an individualperson. As the anti-theft means functions to prevent the engine fromstarting up and output an alarm signal in cases where an engine key thatdoes not permit identification of an individual has been used, theft ofa construction machine by use of an unauthorized engine key can reliablybe prevented.

[0026] The anti-theft means of a construction machine according to yetanother feature of the present invention is designed to force the engineto stop and output an alarm signal when the construction machine fromwhich the engine key has been removed is no longer in a given, properparking posture as a result of unauthorized start-up of the engine. Withthe configuration as above, should the engine be started up byconnecting the battery directly to the starter motor or by any otherunauthorized means, the anti-theft means function to force the engine tostop and output an alarm signal when the construction machine becomesout of a proper parking posture. Therefore, the construction machine isreliably protected against theft.

[0027] The anti-theft means of a construction machine according to yetanother feature of the present invention is an anti-theft unit adaptedto output an alarm signal in cases where the upper structure is not in agiven, proper parking posture when the engine key is removed, saidanti-theft unit being provided with a unit mounting portion, in whichthe anti-theft unit is installed, and a cover for closing off the unitmounting portion from underneath, the unit mounting portion beingprovided at such a location that it is inside the bottom portion of theupper structure and faces the undercarriage when the machine body is ina given, proper parking posture. As an alarm signal is output when theupper structure is not in a proper parking posture, an operator isalways obliged to put the upper structure in a proper parking posturewhen parking the construction machine. When the upper structure is in aproper parking posture, there is only a slight gap between theundercarriage and the cover, which closes off the unit mounting portionfor mounting the anti-theft unit. As the presence of the undercarriagemakes it difficult to remove the cover or the anti-theft unit, theconstruction machine is protected against theft which could otherwiseoccur by the removal of the anti-theft unit.

[0028] A construction machine according to yet another feature of thepresent invention includes a machine body having an identification code,an identification code input means for inputting an identification codeof an operator of the machine body, a posture detecting means fordetecting a posture of the machine body, a posture storage means forstoring the posture of the machine body at the time the machine isparked, a determining means for comparing output from the posturedetecting means and output from the posture storage means so as todetermine whether the machine body has been actuated, a collating meansfor collating the identification code of the operator, which has beenread according to a result of determination of actuation of the machinebody by the determining means, with the identification code of themachine body, and a machine stopping means for forcing the machine bodyto stop when the result of collation by the collating means has provento not match. When the determining means ascertains, as a result ofcomparison of output from the posture detecting means with output fromthe posture storage means, that the machine body has been actuated, thecollating means automatically functions to collate the identificationcode of the operator with the identification code of the machine body.Should the result of collation by the collating means prove to notmatch, the machine stopping means forces the machine body to stop,because it can be assumed that the machine body is being moved by someunauthorized means. The invention is thus effective in reducing thepossibility of theft of the construction machine, compared withconventional art.

[0029] A construction machine according to yet another feature of thepresent invention includes an alarm output means for outputting an alarmwhen the result of collation by the collating means has proven to notmatch. With the configuration as above, should the result of collationby the collating means prove to not match, the anti-theft system of theinvention causes the machine stopping means to force the machine body tostop and the alarm output means to output an alarm, thereby reliablypreventing theft of the construction machine.

[0030] According to yet another feature of the present invention, themachine body of the construction machine includes a work arm which isadapted to be operated vertically and provided with at least onehydraulic actuator for operating the work arm; said hydraulic isprovided with a pressure detector for detecting whether the distal endof the work arm is in contact with the ground; the posture detectingmeans is provided at such a location as to be able to detect the postureof the work arm; and the alarm output means serves to output an alarmwhen the pressure detector detects that the distal end of the work armis not in contact with the ground when the machine body is in the parkedstate. As the machine stopping means forces the machine body to stopalso when the work arm is operated by some unauthorized means, theinvention is effective in reducing the possibility of theft of theconstruction machine, compared with conventional art. Furthermore,unless the distal end of the work arm in properly in contact with theground, the alarm output means outputs an alarm when the machine isparked. The invention thus ensures that the construction machine is in asecure posture when in the parked state, with the end of the work armresting on the ground.

[0031] A construction machine according to yet another feature of thepresent invention includes a machine body having an identification code,an identification code input means for inputting an identification codeof an operator of the machine body, an engine which serves as a powersource for the machine body, an engine rotation detector for detectingrotation of the engine, a determining means for ascertaining build-up ofengine rotation based on a result of detection by the engine rotationdetector, a collating means for collating the identification code of anoperator, which has been read according to a result of determination bythe determining means of build-up of engine rotation, with theidentification code of the machine body, and a machine stopping meansand an alarm output means which are respectively adapted to force themachine body to stop and output an alarm when the result of collation bythe collating means has proven to not match. When the determining meansascertains build-up of engine rotation, the collating meansautomatically functions to collate the identification code of theoperator with the identification code of the machine body. Should it beascertained that the identification codes do not match as a result ofcollation, it can be assumed that the engine is started up by someunauthorized means, such as connecting the battery directly to thestarter motor. In such a case, therefore, the machine stopping meansforces the machine body to stop, while the alarm output means outputs analarm so that theft of the construction machine can be reliablyprevented.

[0032] According to yet another feature of the present invention, theconstruction machine is provided with an engine controller, which servesto control rotation of the engine, and an anti-theft unit which includesat least a determining means and a collating means, wherein theaforementioned engine rotation detector is connected to the enginecontroller via the anti-theft unit. With the configuration as above,signals from the engine speed detector are input into the enginecontroller via the anti-theft unit. Therefore, should the anti-theftunit be removed or the cable be cut, the start-up of the engine would bedisabled. The anti-theft system of the invention is thus capable ofpreventing theft of the construction machine which could otherwise beeffected by cutting the cable or removing the anti-theft unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a circuit diagram showing an anti-theft system employedin a construction machine according to a first embodiment of the presentinvention;

[0034]FIG. 2 is a control block diagram of an anti-theft unit of saidanti-theft system;

[0035]FIG. 3 is a front view of a hydraulic excavator which serves as aconstruction machine using said anti-theft system;

[0036]FIG. 4 is a plan view illustrating how the anti-theft unit and anangle detector of said hydraulic excavator are installed;

[0037]FIG. 5 is an enlarged front view of the operator's cab of saidhydraulic excavator to illustrate how the anti-theft unit is installed;

[0038]FIG. 6 is a circuit diagram showing an anti-theft system employedin a construction machine according to a second embodiment of thepresent invention;

[0039]FIG. 7 is a control block diagram of an anti-theft unit of saidanti-theft system;

[0040]FIG. 8 is an enlarged front view of the operator's cab of ahydraulic excavator which serves as a construction machine using saidanti-theft system, the drawing illustrating how the anti-theft unit andan angle detector of said hydraulic excavator are installed;

[0041]FIG. 9 is a circuit diagram showing an anti-theft system employedin a construction machine according to a third embodiment of the presentinvention;

[0042]FIG. 10 is a control block diagram of an anti-theft unit of saidanti-theft system;

[0043]FIG. 11 is a circuit diagram of an example of an anti-theft systememployed in a conventional construction machine;

[0044]FIG. 12 is a control block diagram of an anti-theft unit of saidanti-theft system; and

[0045]FIG. 13 is a circuit diagram showing an example of a hydrauliccircuit of a hydraulic excavator.

PREFERRED EMBODIMENT OF THE INVENTION

[0046] Next, the present invention is explained in detail, referring toa first embodiment thereof shown in FIGS. 1 through 5, a secondembodiment shown in FIGS. 6 through 8, and a third embodiment shown inFIGS. 9 and 10.

[0047] First, the first embodiment shown in FIGS. 1 through 5 isexplained hereunder. FIG. 1 shows an example of a circuit of ananti-theft system incorporated in a construction machine. FIG. 2 shows acontrol block diagram of a control unit of its anti-theft unit. FIGS. 3through 5 show the structure of a hydraulic excavator and how theanti-theft unit and an angle detector are installed.

[0048] Referring to FIG. 1, the circuit configuration of variouscomponents of the hydraulic excavator is the same as the circuitaccording to the conventional art shown in FIG. 11. Therefore, elementscorresponding to those in FIG. 11 are identified with the same referencenumerals, and explanation thereof is omitted herein.

[0049] The anti-theft system shown in FIG. 1 includes an anti-theft unit31, which serves as an anti-theft means, a starter switch 10, and anantenna 6 serving as a key-removal detecting means. The antenna 6 isincorporated in the starter switch 10 and connected to the anti-theftunit 31. The starter switch 10 is adapted to be turned with an enginekey 8. An identification tag 7 (the term ‘identification’ willhereinafter be abbreviated as ‘ID’) for identifying an individual isattached to the engine key 8. The ID tag 7 serves as an identificationcode input means for automatically inputting into the anti-theft unit 31the ID code of an operator of the machine.

[0050] The anti-theft unit 31 includes a control unit 32, a power supplyunit 3, and relays 4,5,33,34 adapted to be controlled by output from thecontrol unit 32.

[0051] An angle detector 35, which serves as a posture detecting meansfor detecting a rotated posture, i.e. a rotation angle, is connected tothe control unit 32. An engine stop relay 36 is connected to the relay33. An engine stop valve 37 for interrupting fuel to the engine isconnected to the engine stop relay 36. An alarm unit 38 is connected tothe relay 34.

[0052] The relay 33, the engine stop relay 36, and the engine stop valve37 together form a machine stopping means for forcing the machine tostop. The relay 34 and the alarm unit 38 together form an alarm outputmeans for outputting an alarm.

[0053] As the function of the anti-theft system to check the ID code ofthe ID tag 7 and activate the engine start-up relay 12 and the solenoidvalve relay 13 is the same as that of the conventional art shown in FIG.12, its explanation is omitted herein. Only a control arithmetic circuitof the invention is shown in FIG. 2.

[0054]FIG. 2 shows a control block diagram of the anti-theft unit 32,which is adapted to receive signals from the angle detector 35, ACCcontact signals from the starter switch 10, and, via the antenna 6, theID code of the ID tag 7.

[0055] The angle detector 35 is connected to an angle determining unit40, which serves to output ON/OFF signals based on signals output fromthe angle detector 35. To be more specific, it outputs an OFF signal(representing a 0 in a logical circuit) when an angle is within a givenrange, and an ON signal (representing a 1 in a logical circuit) when anangle is outside the given range.

[0056] ID code determining units 41,42 are connected to the antenna 6.An ID code storage unit 43 is connected to the ID code determining units41,42.

[0057] The ID code determining unit 41 is designed to read an ID codewhen the angle determining unit 40 is on and collate the ID code thathas been read with the ID code in the ID code storage unit 43. In caseswhere the ID code determining unit 41 does not recognize an ID code orascertains that the two ID codes do not match, the ID code determiningunit 41 outputs an ON signal. When a match is ascertained, the ID codedetermining unit 41 outputs an OFF signal.

[0058] The ID code determining unit 42 is designed to read an ID codewhen the ACC contact is in the disconnected state and collate the IDcode that has been read with the ID code in the ID code storage unit 43.In cases where the ID code determining unit 42 does not recognize an IDcode or ascertains that the two ID codes do not match, the ID codedetermining unit 42 outputs an ON signal. When a match is ascertained,the ID code determining unit 41 outputs an OFF signal.

[0059] The angle determining unit 40 and the ID code determining unit 42are connected to input terminals of an AND computing unit 44. Therespective output terminals of the AND computing unit 44 and the ID codedetermining unit 41 are connected to a timer 45. The timer 45 serves tooutput an ON signal for a given period of time upon receiving an ONsignal from either the ID code determining unit 41 or the AND computingunit 44.

[0060] The ID code determining unit 41 is connected to the relay 33,which is provided to activate the engine stop relay 36. The timer 45 isconnected to the relay 34, which is provided to activate the alarm unit38.

[0061]FIGS. 3 and 4 respectively represent a front view and a plan viewof the hydraulic excavator. FIG. 5 is an enlarged view of the part whereits operator's cab is located.

[0062] Referring to FIGS. 3, 4, and 5, numeral 50 denotes anundercarriage. An upper structure 51 is rotatably mounted on theundercarriage 50. A work arm 52 is secured to the upper structure 51 bya shaft in such a manner that the work arm 52 is able to swingvertically. The upper structure 51 also includes an operator's cab 53.These components together form a machine body 55.

[0063] As shown in FIG. 4, the undercarriage 50 has protruding plates 54f,54 r, which are respectively located at the front and back of theportion where the undercarriage 50 is connected to the upper structure51. The upper structure 51 is provided with the angle detector 35described above so that the orientation of the work arm 52 can bedetected by the angle detector 35.

[0064] As shown in FIG. 5, the anti-theft unit 31 is installed in a unitmounting portion 30, which is open at the bottom and located at the baseof the operator's cab 53. The unit mounting portion 30 may desirably belocated above the undercarriage 50 when the machine is parked in such aposture as shown in FIG. 4. The underside of the unit mounting portion30 is closed off by a cover 56.

[0065] The work arm 52 is adapted to be swung vertically by hydraulicactuators, i.e. hydraulic cylinders 57 provided between the upperstructure 51 and the work arm 52.

[0066] Next, the function of the first embodiment is explained. As thecircuit shown in FIG. 1 has the same function of starting the engine asin the case of the conventional art described above, its explanation isomitted herein. Therefore, the function concerning the present inventionwill now be explained.

[0067] (1) When the Construction Machine is Stopped, and the Engine Keyis Removed

[0068] Referring to FIG. 1, an explanation is given of the function ofthe first embodiment when the starter switch 10 is turned off to stopthe construction machine, and the engine key 8 is pulled out of thestarter switch 10 and moved away from the antenna 6.

[0069] Turning off the starter switch 10 cuts off the ACC contact,thereby activating the ID code determining unit 42.

[0070] The ID code determining unit 42 is designed to read an ID codewhen the ACC contact is in the disconnected state and collate the IDcode that has been read with the ID code in the ID code storage unit 43.In cases where the ID code determining unit 42 does not recognize an IDcode or ascertains that the two ID codes do not match, the ID codedetermining unit 42 outputs an ON signal. When a match is ascertained,the ID code determining unit 41 outputs an OFF signal.

[0071] Therefore, turning off the starter switch 10 and removing theengine key 8 from the starter switch 10 and moving the engine key 8 awayfrom the antenna 6 causes the ID code determining unit 42 to output anON signal, because the ID code determining unit 42 becomes unable toread the ID code.

[0072] In cases where the work arm 52 is oriented straight forward orrearward with respect to the traveling direction as shown in FIG. 4, theangle detector 35 detects the protrusion plate 54 f or the protrusionplate 54 r so that the angle determining unit 40 outputs an OFF signal.When the work arm 52 is oriented neither straight forward nor rearwardwith respect to the traveling direction, the angle determining unit 40outputs an ON signal, because the angle detector 35 is unable to detecteither protrusion plate 54 f,54 r.

[0073] Signals from the angle determining unit 40 and the ID codedetermining unit 42 are input into the AND computing unit 44, whichcarries out a logical product operation. The result of the operation isthen output from the AND computing unit 44 and activates the relay 34via the timer 45.

[0074] Therefore, when the engine key 8 is removed from the starterswitch 10 in the state that the machine is not in a given, properparking posture, with the work arm 52 being oriented neither straightforward nor rearward, both the angle determining unit 40 and the ID codedetermining unit 42 output ON signals so that the AND computing unit 44outputs an ON signal, thereby energizing the relay 34 via the timer 45.As a result, the alarm unit 38 is activated to call the operator'sattention.

[0075] (2) When the Construction Machine is Operated with the EngineBeing Started by an Unauthorized Means

[0076] An explanation is given of a situation where the constructionmachine is operated with the power source of the machine body 55, i.e.the engine 22, being started by connecting the plus line of the battery9 directly to the starter motor 15.

[0077] When the engine 22 is started and the construction machine is putinto operation to move the upper structure 51, the angle determiningunit 40 is turned on, and the ID code determining unit 41 is activated.

[0078] The ID code determining unit 41 is designed to output an ONsignal or an OFF signal as a result of its function of reading an IDcode; in cases where no ID code has been received or the ID code thathas been read does not correspond to the ID code in the ID code storageunit 43, the ID code determining unit 41 outputs an ON signal. When amatch is ascertained, the ID code determining unit 41 outputs an OFFsignal.

[0079] Therefore, should the upper carriage 51 be moved as a result ofoperation of the construction machine by an unauthorized means, the IDcode determining unit 41 outputs an ON signal to activate the enginestop valve 37, via the relay 33 and the engine stop relay 36. As theengine stop valve 37 interrupts the fuel to the engine 22, the engine 22stops.

[0080] Meanwhile, the relay 34 is energized via the timer 45 so that thealarm unit 38 is activated to sound an alarm. Thus, theft of the machineis prevented.

[0081] (3) When an Engine Key that Does Not Permit Identification of anIndividual is Used

[0082] Should any engine key other than an engine key 8 that permitsidentification of an individual by means of an ID tag 7 is used, the IDcode determining unit 41 outputs an ON signal to activate the enginestop valve 37 via the relay 33 and the engine stop relay 36, therebypreventing the engine 22 from starting up. Meanwhile, the ON signaloutput from the ID code determining unit 41 also causes the timer 45 tooutput an ON signal, i.e. an alarm signal, for a given period of time sothat the alarm unit 38 is activated by the relay 34.

[0083] The features described above offer benefits as follows:

[0084] (1) The anti-theft unit is designed so that an alarm is outputwhen the construction machine is going to be parked in a posture wherethe work arm 52 is not parallel with the traveling direction. Therefore,it is always necessary for an operator who is parking the constructionmachine to position the machine so that the work arm 52 is parallel withthe traveling direction. As shown in FIG. 5, when the machine is in sucha posture, there is only a slight gap between the undercarriage 50 andthe cover 56, which closes off the unit mounting portion 30 of theanti-theft unit 31. The lack of sufficient clearance makes it difficultto remove the cover 56 or the anti-theft unit 31 and consequentlyprevents theft or unauthorized removal of the anti-theft unit 31.

[0085] (2) Should the upper structure 51 be operated with the engine 22being started by an unauthorized means, the anti-theft system stops theengine and outputs an alarm, thereby preventing unauthorized start-up ofthe engine 22 and resultant theft of the machine.

[0086] (3) Should an engine key that does not permit identification ofan individual be used, the anti-theft unit 31 functions to prevent theengine 22 from starting and output an alarm signal to the alarm unit 38.Thus, theft of a construction machine by use of an unauthorized enginekey can reliably be prevented.

[0087] Next, the second embodiment shown in FIGS. 6 through 8 isexplained hereunder. FIG. 6 shows an example of a circuit of ananti-theft system incorporated in a construction machine. FIG. 7 shows acontrol block diagram of its anti-theft unit. FIG. 8 shows how an angledetector and a pressure detector are installed in a hydraulic excavator.

[0088] In these drawings, the circuit configuration of variouscomponents of the hydraulic excavator is the same as the circuitaccording to the conventional art shown in FIG. 11. Therefore, elementscorresponding to those in FIG. 11 are identified with the same referencenumerals, and their explanation is omitted herein.

[0089] The anti-theft system shown in FIG. 6 includes an anti-theft unit61, a starter switch 10, and an antenna 6 which is incorporated in thestarter switch 10 and connected to the anti-theft unit 61. The starterswitch 10 is adapted to be turned with an engine key 8. An ID tag 7 foridentifying an individual is attached to the engine key 8. The ID tag 7serves as an identification code input means for automatically inputtinginto the anti-theft unit 61 the ID code of an operator of the machine.

[0090] The anti-theft unit 61 includes a control unit 62, a power supplyunit 3, and relays 4,5,33,34 which are adapted to be controlled byoutput from the control unit 62.

[0091] An angle detector 63, which serves as a posture detecting meansfor detecting a posture of the machine body 55 is connected to thecontrol unit 62. The term “posture of the machine body 55” means atilted posture, i.e. an angle, of the work arm 52. Also connected to thecontrol unit 62 is a pressure detector 64 for detecting pressure in thehead-side of one of the hydraulic cylinders 57. The hydraulic cylinders57 are hydraulic actuators for vertically swinging the work arm 52.

[0092] The pressure detector 64 serves to detect whether the distal endof the work arm 52 is in contact with the ground by detecting a state ofpressure in the head-side of the hydraulic cylinder 57 to which thepressure detector 64 is connected; when the pressure in the head-side islow, it is determined that the distal end of the work arm 52 is incontact with the ground.

[0093] An engine stop relay 36 is connected to the relay 33. An enginestop valve 37 for interrupting fuel to the engine is connected to theengine stop relay 36. An alarm unit 38 is connected to the relay 34.

[0094] Referring to FIG. 6, the relay 33, the engine stop relay 36, andthe engine stop valve 37 together form a machine stopping means forforcing the machine to stop. The relay 34 and the alarm unit 38 togetherform an alarm output means for outputting an alarm.

[0095] As the function of the anti-theft system to check the ID code ofthe ID tag 7 and activate the engine start-up relay 12 and the solenoidvalve relay 13 is the same as that of the conventional art shown in FIG.12, its explanation is omitted herein. Only a control arithmetic circuitof the invention is shown in FIG. 7.

[0096]FIG. 7 shows a control block diagram of the anti-theft unit 62,which is adapted to receive signals from the angle detector 63, signalsfrom the pressure detector 64 of the hydraulic cylinder 57, ACC contactsignals from the starter switch 10, and, via the antenna 6, the ID codeof the ID tag 7.

[0097] The angle detector 63 is connected to an angle storage unit 65,which serves as a posture storage means for storing a posture of themachine body 55, in other words a tilted posture, i.e. an angle, of thework arm 52 when the ACC contact is disconnected. The pressure detector64 is connected to a pressure determining unit 66, which serves tooutput an OFF signal when the signal from the pressure detector 64 ofthe hydraulic cylinder 57 represents a pressure not lower than a givenlevel, and an ON signal when the pressure is reduced to less than thegiven level. The angle detector 63 and the angle storage unit 65 areconnected to a comparator 67, which serves as a determining means forcomparing a signal from the angle detector 63 with a signal from theangle storage unit 65 so as to determine whether the machine body 55 hasbeen actuated. The pressure determining unit 66 and the comparator 67are connected to an OR computing unit 68, which serves to compute alogical sum of signals output from the pressure determining unit 66 andthe comparator 67.

[0098] Connected to the antenna 6 are ID code determining units 69,70,which together serve as a collating means for collating anidentification code of an operator of the machine and the ID code of themachine body 55. An ID code storage unit 71 which stores the ID codeattached to the machine body 55 is connected to the ID code determiningunits 69,70.

[0099] The ID code determining unit 69 is designed to read an ID codewhen the OR computing unit 68 is on, and collate the ID code that hasbeen read with the ID code in the ID code storage unit 71. In caseswhere the ID code determining unit 69 does not recognize an ID code orascertains that the two ID codes do not match, the ID code determiningunit 69 outputs an ON signal. When a match is ascertained, the ID codedetermining unit 69 outputs an OFF signal.

[0100] The ID code determining unit 70 is designed to read an ID codewhen the ACC contact is in the disconnected state and collate the IDcode that has been read with the ID code in the ID code storage unit 71.In cases where the ID code determining unit 70 does not recognize an IDcode or ascertains that the two ID codes do not match, the ID codedetermining unit 70 outputs an ON signal. When a match is ascertained,the ID code determining unit 70 outputs an OFF signal.

[0101] The pressure determining unit 66 and the ID code determining unit70 are connected to input terminals of an AND computing unit 72. Therespective output terminals of the AND computing unit 72 and the ID codedetermining unit 69 are connected to a timer 73. The timer 73 serves tooutput ON signals for a given period of time upon receiving an ON signalfrom either the ID code determining unit 69 or the AND computing unit72.

[0102] The ID code determining unit 69 is connected to the relay 33,which serves to activate the engine stop relay 36. The timer 73 isconnected to the relay 34, which serves to activate the alarm unit 38.

[0103] As shown in FIG. 8, the angle detector 63 is located at therocking joint portion of the work arm 52. The pressure detector 64 isprovided at the head-side of one of the hydraulic cylinders 57 thatdrive the work arm 52. The pressure detector 64 serves to detect whatstate the arm 52 is in when the construction machine is in the parkedstate.

[0104] Next, the function of the second embodiment is explained. As thecircuit shown in FIG. 6 has the same function of starting the engine asin the case of the conventional art described above, its explanation isomitted herein. Therefore, the function concerning the present inventionwill now be explained.

[0105] (1) When the Construction Machine is Stopped, and the Engine Keyis Removed

[0106] Referring to FIG. 6, an explanation is given of the function ofthe second embodiment when the starter switch 10 is turned off to stopthe construction machine, and the engine key 8 is pulled out of thestarter switch 10 and moved away from the antenna 6.

[0107] Turning off the starter switch 10 cuts off the ACC contact,thereby activating the ID code determining unit 70 shown in FIG. 7.

[0108] The ID code determining unit 70 is designed to read an ID codewhen the ACC contact is in the disconnected state and collate the IDcode that has been read with the ID code in the ID code storage unit 71.In cases where the ID code determining unit 70 does not recognize an IDcode or ascertains that the two ID codes do not match, the ID codedetermining unit 70 outputs an ON signal. When a match is ascertained,the ID code determining unit 70 outputs an OFF signal.

[0109] Therefore, turning off the starter switch 10 and removing theengine key 8 from the starter switch 10 and moving the engine key 8 awayfrom the antenna 6 causes the ID code determining unit 70 to output anON signal.

[0110] Meanwhile, the pressure detector 64 shown in FIG. 8 detects thepressure in the head-side of the hydraulic cylinder 57 to which thepressure detector 64 is attached.

[0111] When the distal end of the work arm 52 is fully in contact withthe ground, the pressure in the head-side of the hydraulic cylinder 57is low. Therefore, the pressure determining unit 66 outputs an OFFsignal.

[0112] When the distal end of the work arm 52 is not in contact with theground, the pressure determining unit 66 outputs an ON signal, becausethe pressure in the head-side of the hydraulic cylinder 57 remains high.

[0113] Based on outputs of the pressure determining unit 66 and the IDcode determining unit 70, the AND computing unit 72 carries out alogical product operation and outputs the result of the operation,thereby activating the relay 34 via the timer 73.

[0114] Therefore, when the engine key 8 is removed from the constructionmachine which is parked in the state that the end of the work arm 52 isnot in full contact with the ground, both the pressure determining unit66 and the ID code determining unit 70 output ON signals so that the ANDcomputing unit 72 outputs an ON signal, thereby energizing the relay 34via the timer 73. As a result, the alarm unit 38 is activated to warnthe operator that the end of the work arm 52 is not in contact with theground.

[0115] (2) When the Construction Machine is Operated with the EngineBeing Started by an Unauthorized Means

[0116] An explanation is given of a situation where the constructionmachine is improperly operated by connecting the plus line of thebattery 9 directly to the starter motor 15 to start the engine 22.

[0117] When the work arm 52 is moved, the comparator 67 compares thesignal from the angle detector 63 of the work arm 52 with the valuestored in the angle storage unit 65.

[0118] As the angle of the work arm 52 at the time the starter switch 10was turned off is stored in the angle storage unit 65, the comparator 67ascertains that the work arm 52 has been moved.

[0119] Meanwhile, based on the state of pressure of the hydrauliccylinder 57, the pressure determining unit 66 determines whether the endof the work arm 52 is in full contact with the ground.

[0120] Therefore, when the work arm 52 is moved, the comparator 67 orthe pressure determining unit 66 outputs an ON signal, which causes theOR computing unit 68 to output and ON signal, thereby activating the IDcode determining unit 69.

[0121] The ID code determining unit 69 is designed to read an ID codeand output an ON signal or an OFF signal as a result of its function ofreading an ID code and collating it with the ID cored in the ID codestorage unit 71; in cases where no ID code has been received or the twoID codes do not match, the ID code determining unit 69 outputs an ONsignal. When a match is ascertained, the ID code determining unit 69outputs an OFF signal. Therefore, should the work arm 52 be moved bystarting the engine 22 by an unauthorized means, the ID code determiningunit 69 outputs an ON signal to activate the relay 34 via the relay 33and the timer 73. The activated relay 34 then activates the engine stopvalve 37 via the engine stop relay 36. The engine stop valve 37 stopsthe engine 22 by interrupting the fuel to the engine 22, while the alarmunit 38 is activated to sound an alarm to notify those who are in thevicinity of an attempt of theft.

[0122] (3) When an Engine Key that Does Not Permit identification of anIndividual is Used

[0123] Should any engine key other than an engine key 8 that permitsidentification of an individual by means of an ID tag 7 is used, the IDcode determining unit 69 outputs an ON signal to activate the enginestop valve 37 via the relay 33 and the engine stop relay 36, therebypreventing the engine 22 from starting up. Meanwhile, the ON signaloutput from the ID code determining unit 69 also causes the timer 73 tooutput an ON signal, i.e. an alarm signal, for a given period of time sothat the alarm unit 38 is activated by the relay 34.

[0124] Next, the effects of the second embodiment is described.

[0125] The features described above offer benefits as follows:

[0126] (1) Should the distal end of the work arm 52 be not in contactwith the ground at the time of parking, in other words when the enginekey 8 is removed after the construction machine is stopped, an alarm isoutput. With the configuration as above, the system ensures safety bythus requiring the end of the work arm 52 to be in full contact with theground when the machine is parked.

[0127] (2) Should the work arm 52 be operated with the engine 22 beingstarted by an unauthorized means, the anti-theft system outputs ansignal to stop the engine and sound an alarm. Therefore, compared withconventional anti-theft systems, the anti-theft system of the secondembodiment is less vulnerable to theft.

[0128] (3) Should an engine key that does not permit identification ofan individual be used, the anti-theft unit 61 functions to prevent theengine 22 from starting up and output an alarm signal to the alarm unit38. Thus, theft of a construction machine by use of an unauthorizedengine key can reliably be prevented.

[0129] Next, the third embodiment shown in FIGS. 9 and 10 is explainedhereunder. FIG. 9 shows an example of a circuit of an anti-theft systemincorporated in a construction machine. FIG. 10 shows a control blockdiagram of its anti-theft unit.

[0130] Referring to FIG. 9, the circuit configuration of variouscomponents of the hydraulic excavator is the same as the circuitaccording to the conventional art shown in FIG. 11. Therefore, elementscorresponding to those in FIG. 11 are identified with the same referencenumerals, and their explanation is omitted herein.

[0131] The anti-theft system shown in FIG. 9 includes an anti-theft unit81, a starter switch 10, and an antenna 6 which is incorporated in thestarter switch 10 and connected to the anti-theft unit 81. The starterswitch 10 is adapted to be turned with an engine key 8. An ID tag 7 foridentifying an individual is attached to the engine key 8. The ID tag 7serves as an identification code input means for inputting into theanti-theft unit 81 the ID code of an operator of the machine.

[0132] The anti-theft unit 81 includes a control unit 82, a power supplyunit 3, and relays 4,5,33,34 which are adapted to be controlled byoutput from the control unit 82.

[0133] An engine controller 84 is connected to the speed governingsection of the engine 22. The engine controller 84 is provided tocontrol the engine 22 to a given engine speed, which is set by using anaccelerator dial 83. An engine speed detector 85 for detecting theengine speed of the engine 22 is connected to the control unit 82. Theengine speed detector 85 is also connected to the engine controller 84by a cable which is branched inside the anti-theft unit 81.

[0134] As the function of the anti-theft system to check the ID code ofthe ID tag 7 and activate the engine start-up relay 12 and the solenoidvalve relay 13 is the same as that of the conventional art shown in FIG.12, its explanation is omitted herein. Only a control arithmetic circuitof the invention is shown in FIG. 10.

[0135]FIG. 10 shows a control block diagram of the anti-theft unit 82,which is adapted to receive signals from the engine speed detector 85,ACC contact signals from the starter switch 10, and, via the antenna 6,the ID code of an ID tag 7.

[0136] A rotation determining unit 86 which serves as a determiningmeans for ascertaining build-up of engine rotation is connected to theengine speed detector 85. The rotation determining unit 86 performs thisfunction based on results of detection by the engine speed detector 85.To be more specific, the rotation determining unit 86 serves to read asignal from the engine speed detector 85 so as to output an OFF signalwhen the engine speed is lower than a given speed, and an ON signal atall other times.

[0137] An ID code determining unit 87 which serves as a collating meansis connected to the antenna 6. An ID code storage unit 88 is connectedto the ID code determining unit 87.

[0138] The ID code determining unit 87 is designed to read an ID codefrom an ID tag 7 via the antenna 6 when the output from the rotationdetermining unit 86 is on and collate the ID code that has been readwith the ID code in the ID code storage unit 88. In cases where the IDcode determining unit 87 does not recognize an ID code or ascertainsthat the two ID codes do not match, the ID code determining unit 87outputs an ON signal. When a match is ascertained, the ID codedetermining unit 87 outputs an OFF signal.

[0139] A timer 89 is connected to the ID code determining unit 87. Thetimer 89 serves to output an ON signal for a given period of time uponreceiving an ON signal from the ID code determining unit 87.

[0140] The ID code determining unit 87 is connected to the relay 33,which serves to activate the engine stop relay 36. The timer 89 isconnected to the relay 34, which serves to activate the alarm unit 38.

[0141] Referring to FIG. 9, the relay 33, the engine stop relay 36, andthe engine stop valve 37 together form a machine stopping means forforcing the machine to stop. The relay 34 and the alarm unit 38 togetherform an alarm output means for outputting an alarm.

[0142] Next, the function of the third embodiment is explained. As thecircuit shown in FIG. 9 has the same function of starting up the engineas in the case of the conventional art described above, its explanationis omitted herein. Therefore, the function concerning the presentinvention will now be explained.

[0143] (1) When the Construction Machine is Operated with the EngineBeing Started by an Unauthorized Means

[0144] An explanation is given of a situation where the constructionmachine is improperly operated by connecting the plus line of thebattery 9 directly to the starter motor 15 to start the engine 22.

[0145] Upon build-up of engine rotation, the rotation determining unit86 outputs an ON signal to activate the ID code determining unit 87.

[0146] The ID code determining unit 87 is designed to output an ONsignal or an OFF signal as a result of its function of reading an IDcode and collating it with the ID code stored in the ID code storageunit 88; in cases where no ID code has been received or the two ID codesdo not match, the ID code determining unit 87 outputs an ON signal. Whena match is ascertained, the ID code determining unit 87 outputs an OFFsignal.

[0147] In other words, should the engine 22 be started by anunauthorized means, the ID code determining unit 87 outputs an ONsignal. This means that starting the engine 22 by the plus line of thebattery 9 directly to the starter motor 15 causes the ID codedetermining unit 87 to outputs an ON signal.

[0148] As a result, the engine stop valve 37 is activated via the relay33 and the engine stop relay 36 so that the engine stop valve 37interrupts the fuel to the engine 22 so as to stop the engine 22.Meanwhile, the ON signal output from the ID code determining unit 87also energizes the relay 34 via the timer 89, thereby activating alarmunit 38 to notify those who are in the vicinity of an attempt of theft.

[0149] (2) When an Engine Key that Does Not Permit Identification of anIndividual is Used

[0150] Should any engine key other than an engine key 8 that permitsidentification of an individual by means of an ID tag 7 is used, the IDcode determining unit 87 outputs an ON signal to activate the enginestop valve 37 via the relay 33 and the engine stop relay 36, therebypreventing the engine 22 from starting up. Meanwhile, the ON signaloutput from the ID code determining unit 87 also causes the timer 89 tooutput an ON signal, i.e. an alarm signal, for a given period of time sothat the alarm unit 38 is activated by the relay 34.

[0151] (3) When the Anti-Theft Unit is Removed

[0152] As shown in FIG. 9, the anti-theft system of the third embodimenthas such a configuration that signals from the engine speed detector 85are input into the anti-theft unit 81, from which signals are output tothe engine controller 84. Therefore, should the anti-theft unit 81 beremoved or the cable be cut, the start-up of the engine 22 would bedisabled, making theft of the machine difficult.

[0153] Next, the effects of the third embodiment is described.

[0154] The features described above offer benefits as follows:

[0155] (1) Should the engine 22 be started by connecting the plus lineof the battery 9 directly to the starter motor 15, the anti-theft systemoutputs a signal to stop the engine and sound an alarm. Thus, theft ofthe construction machine by use of an unauthorized means can beprevented.

[0156] (2) Should an engine key that does not permit identification ofan individual be used, the anti-theft unit 81 functions to prevent theengine 22 from starting and output an alarm signal to the alarm unit 38.Thus, theft of a construction machine by use of an unauthorized enginekey can reliably be prevented.

[0157] (3) Signals from the engine speed detector 85 are input into theengine controller 84 via the anti-theft unit 81. Therefore, should theanti-theft unit 81 be removed or the cable be cut, the start-up of theengine 22 would be disabled. The anti-theft system of the thirdembodiment is thus capable of preventing theft of the constructionmachine which could otherwise be effected by cutting a cable or removingthe anti-theft unit 81.

POSSIBLE INDUSTRIAL APPLICATION

[0158] The present invention is applicable to not only hydraulicexcavators but also other construction machines, such as loaders andbulldozers.

1. A construction machine including: a machine body; an engine thatserves as a power source for the machine body; a key-removal detectingmeans for detecting removal of the engine key after the engine isstopped; a posture detecting means for detecting a posture of themachine body; and an anti-theft means adapted to output an alarm signalin cases where the machine body from which the engine key has beenremoved is not in a given, proper parking posture.
 2. A constructionmachine including: an undercarriage; an upper structure rotatablymounted on the undercarriage; an engine that serves as a power sourcefor the undercarriage and the upper structure; a key-removal detectingmeans for detecting removal of the engine key after the engine isstopped; a posture detecting means for detecting a rotated posture ofthe upper structure; and an anti-theft means adapted to output an alarmsignal in cases where the upper structure from which the engine key hasbeen removed is not in a given, proper parking posture.
 3. Aconstruction machine as claimed in claim 1 or claim 2, wherein: theanti-theft means is designed to prevent the engine from starting up andoutput an alarm signal when any engine key other than an engine key thatpermits identification of an individual person.
 4. A constructionmachine as claimed in claim 1 or claim 2, wherein: the anti-theft meansis designed to force the engine to stop and output an alarm signal whenthe construction machine from which the engine key has been removed isno longer in a given, proper parking posture as a result of unauthorizedstart-up of the engine.
 5. A construction machine as claimed in any oneof the claims from claim 2 to claim 4, wherein: the anti-theft means isan anti-theft unit adapted to output an alarm signal in cases where theupper structure is not in a given, proper parking posture when theengine key is removed, said anti-theft unit being provided with: a unitmounting portion in which the anti-theft unit is installed and which isprovided at such a location that it is inside the bottom portion of theupper structure and faces the undercarriage when the machine body is ina given, proper parking posture, and a cover for closing off the unitmounting portion from underneath.
 6. A construction machine including: amachine body having an identification code; an identification code inputmeans for inputting an identification code of an operator of the machinebody; a posture detecting means for detecting a posture of the machinebody; a posture storage means for storing the posture of the machinebody at the time the machine is parked; a determining means forcomparing output from the posture detecting means and output from theposture storage means so as to determine whether the machine body hasbeen actuated; a collating means for collating the identification codeof the operator, which has been read according to a result ofdetermination of actuation of the machine body by the determining means,with the identification code of the machine body; and a machine stoppingmeans for forcing the machine body to stop when the result of collationby the collating means has proven to not match.
 7. A constructionmachine as claimed in claim 6, wherein: the construction machineincludes an alarm output means for outputting an alarm when the resultof collation by the collating means has proven to not match.
 8. Aconstruction machine as claimed in claim 7, wherein: the machine bodyincludes a work arm which is adapted to be operated vertically; saidwork arm is provided with at least one hydraulic actuator for operatingthe work arm; said hydraulic actuator is provided with a pressuredetector for detecting whether the distal end of the work arm is incontact with the ground; the posture detecting means is provided at sucha location as to be able to detect the posture of the work arm; and thealarm output means serves to output an alarm when the pressure detectordetects that the distal end of the work arm is not in contact with theground when the machine body is in the parked state.
 9. A constructionmachine including: a machine body having an identification code; anidentification code input means for inputting an identification code ofan operator of the machine body; an engine which serves as a powersource for the machine body; an engine rotation detector for detectingrotation of the engine; a determining means for ascertaining build-up ofengine rotation based on a result of detection by the engine rotationdetector; a collating means for collating the identification code of anoperator, which has been read according to a result of determination bythe determining means of build-up of engine rotation, with theidentification code of the machine body; and a machine stopping meansand an alarm output means which are respectively adapted to force themachine body to stop and output an alarm when the result of collation bythe collating means has proven to not match.
 10. A construction machineas claimed in claim 9, wherein: the machine body includes: an enginecontroller for controlling rotation of the engine, and an anti-theftunit which includes at least a determining means and a collating means;and said engine rotation detector is connected to the engine controllervia the anti-theft unit.